You need to use food grade U.S.P glycerine, this can be relatively hard to find inexpensively but a gallon lasts a LONG time.

Glycerines have a shorter shelf life than alcohol based tinctures and while they can sit on the shelf I refrigerate mine. Vegetable glycerine has nearly no impact on blood sugar or insulin and is very low in calories (4.3 per gram). It's sweet taste makes the tincture more palatable than the alcohol based tincture and is a suitable substitute for those concerned with alcohol consumption.

Add the amount of cannabis that you desire for potency. I added 6 oz of roughly trimmed (finger trimmed the leaves off) cannabis to 1 gallon of glycerine. For your personal preference add more cannabis or less depending on desired potency. I blend mine, using a coffee grinder, blender or if you are lucky enough to have a Vita Mix. Make sure there is no other product matter in whatever you use. I use a clean basting brush to clean out my Vita Mix when I am done powdering my cannabis.

Place in a crockpot on low. Some crockpot's low settings are too high so you may not be able to use yours. A "Keep Warm" setting if you have it is the best choice. Too hot, and you are killing the properties you are trying to extract, you want the mixture to be as warm as possible without boiling, I left my tincture like this for 24 hours. I have heard people leaving the tincture from anywhere from 4-6 hours to 3 days. You can try the tincture at intervals to decide when you are done. REMEMBER that glycerine tincture retains heat VERY WELL, do not burn yourself!!

If you do not have a crockpot you can place the herbs in a clear, sealed jar in a warm, sunny spot and accomplish the same thing over 4 weeks. Some people make their "sunshine tinctures" over 2 weeks. I do not feel that is long enough, especially in colder weather. Some leave them in the sun for up to 12 weeks. I have never seen a need to go that long myself. Shake each day to mix the herbs in.

When ready to strain use cheesecloth and a strainer to extract the cannabis debris, the THC has been extracted and the tincture is ready to use. The best way to store is in a glass amber bottle. A good place to obtain a large bottle for the bulk of your tincture is a brewery store that has supplies to make wine or beer. I also obtained a few small amber bottles with eye droppers for convenience. It takes a lot longer to strain glycerine than it does alcohol, the tincture will drip when strained instead of flow.